


A Working Hypothesis

by rosecake



Category: Star Trek: Discovery
Genre: Alternate Universe - Canon Divergence, F/F, Impersonation, Mirror Universe, Questionable Science Experiments, Sex Pollen, Smut, Stranded in Enemy Territory, Uniforms, drug references
Language: English
Status: Completed
Published: 2019-06-03
Updated: 2019-06-03
Packaged: 2020-04-07 02:11:43
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,063
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19075375
Author URL: https://archiveofourown.org/users/rosecake/pseuds/rosecake
Summary: They’ve been stuck in the Mirror Universe for so long that Tilly, in desperation, gets a little sloppy with some of her mycelial network experiments.





	A Working Hypothesis

**Author's Note:**

  * For [weakinteraction](https://archiveofourown.org/users/weakinteraction/gifts).



The only place Michael hated more in this godforsaken universe than the ISS _Shenzhou_ was the ISS _Discovery_. On the _Shenzhou_ she at least had the illusion of control to comfort her. There was a sense of familiarity there, as uneasy as it was, that made things easier to handle. Even if that familiarity was a sign they’d been stranded in this universe for far too long. She might live in a pit of a vipers, they were still her own vipers to command.

The same could not be said for the _Discovery_. Each ship in this universe operated as its own little fiefdom, and the Captains were encouraged to see each other as competition, not allies. Worse than competition, really - in the Empire anyone as strong as you was an existential threat, to be wiped out at the earliest opportunity.

As Michael walked down the halls of the ship she was actually aware of the crew’s stares. The kindest of them wondered why she was there; the worst of them were sizing her up for an assassination attempt.

That hostility was a burden worth bearing if it meant getting to see Tilly in person, though. So much of her contact with her own people was limited to comms these days - Tilly she met up with rarely, and she hadn’t seen Saru and the others still on the real _Discovery_ face-to-face since taking up her impersonation of Captain Burnham. She shouldn’t need human contact, she’d been raised to be more self-sufficient than that, but deep down she wanted it. Wanted it badly enough to take risks to get it.

And, well, Tilly had called for her. Michael wasn’t going to ignore that no matter what the risk.

It had been a vague message, though, and the uncertainty of the situation wore on Michael’s already thin nerves. By the time she’d made her way from the transporter room to Tilly’s quarters her pulse was elevated, her heart beating hard from the adrenaline. Why hadn’t Tilly met her at the transporter? Was she sick, was she injured? If she didn’t want the crew to see her in whatever state she was in, then calling Michael had been a risk. Her crew was likely already gossiping about the fact that she hadn’t left her quarters to meet a fellow captain.

The guards around Tilly’s door failed to move to let her pass, choosing to silently glare at her instead. Michael fought the urge to sigh. “My presence was requested,” she snapped, and she didn’t have to fake her irritation at being blocked. “Do you mean to disobey your captain?”

The threat of Captain Tilly’s anger managed to move them, and Michael stepped past them when the door opened. It shut behind her, automatically, leaving her standing alone in Tilly’s darkened quarters.

“Captain Tilly,” said Michael, in the coldest and most imperious tone of voice she could muster, even though the door had already closed behind her. The need to keep up appearances ran deep, and it would be a moment or two before she could relax and be her own self again. In this universe, Michael Burnham and Sylvia Tilly were both favored supporters of the Emperor, and that was the extent of their relationship. They weren’t close, and they definitely weren’t friends, and so Michael endeavored to act distant in public.

Someday they’d be roommates again, hopefully, but Michael wasn’t sure how long that would take.

There was no response, and the low lighting in the rooms made her nervous. “Tilly?” she asked, this time letting her concern slip into her voice.

There was a groan from the coach on the far side of the room, and as Michael’s eyesight adjusted to the gloom she realized Tilly was lying on it.

“Michael,” said Tilly, and for a moment it looked like she was going to stand, but instead she only slid off the couch and down to the floor. “Oh, Michael, I’m so glad you’re here.”

Michael rushed over to her, worried that she was injured, that she’d gotten sick some how. What if she’d been poisoned?

“Tilly,” she said, quietly, nearly whispering even though she knew the rooms were quite thoroughly soundproofed. She’d spent so much of the past few months dedicating her life to secrecy that the urge to stay hidden was overpowering. “Are you okay? What happened?”

Tilly was only half dressed, her gold plate missing and her jumpsuit unzipped down to her navel, and her hair had begun a rebellion against the regular straightening she put it through in this universe. It curled erratically around her face, sticking up at odd angles in the back. Her face was flushed, and the naked relief on her face as she reached for Michael did nothing to ease Michael’s concern.

“I’m fine,” said Tilly, clinging to her as Michael helped her back onto the couch. “I mean, I’m not fine at all, really, but I’m not dying. I don’t think I’m dying. Am I dying?”

Up close her pupils were so wide it made her eyes look as black as space. Michael brushed a hand against her forehead, pushing some errant strands of hair back, and she was warm but not hot. If she had a fever it was only a mild one. A proper thermometer would have been more reassuring, but Michael hadn’t brought medical equipment with her and she didn’t want to draw attention by requesting any.

“What happened to you?” asked Michael as Tilly leaned against her, wrapping her arms around her and hugging her tightly. “Tilly, what’s wrong with you?”

“I can see space-time,” said Tilly. Her words were a little slurred, but she sounded adamant, sure of herself. Michael stroked her back reassuringly and she sighed, pressing her face into Michael’s neck. “I can see how to get home, Michael, I just, I can’t- I can’t figure out how to hold onto it, you know?”

“Tilly,” said Michael. She didn’t seem injured, and she didn’t exactly seem poisoned, either. “Tilly, were you drugged?”

“I’m so high, Michael,” said Tilly. It sounded like a confession, like something she was grateful to get off her chest. “Oh, god, I’m so high. I only tried, like, a couple micrograms of it, I was just going to time it out and work my way up, but holy hell. I’m losing it. Stamets’ notes said he was taking whole grams of it at a time, how is he not dead?”

He had ended up comatose, which Michael figured Tilly probably didn’t need to be reminded of at the moment. “What did you take?” she asked, hoping it was a clear enough question to get her a direct answer. If she knew what they were dealing with she might be able to find the notes Tilly had been working with.

“Uh, he called it mycelial dithyoximide?”

Michael had a received a Vulcan education and had a comprehensive understanding of chemistry as a result, and the term _dithyoximide_ didn’t ring any bells. “What?” she asked, uncertain if it was something new to this universe or if Tilly was too intoxicated to remember the correct term. “Do you mean dithiooxamide? Or diethylamide?”

“Yeah, sure,” said Tilly. She was nuzzling Michael’s neck, now, and trying to pull her even closer. “It’s part of the cocktail this Stamets was using to hook into the spore drive. Like acid, basically.”

Michael inhaled deeply. She hated everything about this universe so much. “You’re telling me that this version of Stamets was using LSD as part of the way to access the network?”

“Yes!” Tilly said, sitting up suddenly, smiling broadly in her excitement. “You got it! You’re so smart, Michael. You’re like the smartest person I know. Well, in terms of general smartness. Stamets might be better at, you know, physics specifically. But I like you more.”

“I like you too,” said Michael, and Tilly nestled her face back against her neck. “I think we just need to wait it out. Was there any documentation on it? Anything that might tell us how long the effects last?”

She didn’t like the though of Tilly being this open, this vulnerable for long. Concern had kept her heart elevated - too much adrenaline, and she was beginning to feel noticeably warm from the stress of it. The Imperial uniforms were uncomfortable at the best of time, and she pulled at her collar, trying to ease the pressure around her neck.

“You should just take it off,” mumbled Tilly.

Part of her thought it sounded like a good idea, but she had more pressing concerns at the moment. “Do you know how long it’s supposed to last, Tilly? Try to concentrate.”

“His notes said half a milligram would last around twelve hours, but I didn’t take nearly that much,” said Tilly. Her eyes were closed, and she did look as if she was doing her best to remember clearly. “But it’s been _days_. I was so lonely, Michael! I wanted to call you so bad even though I knew I wasn’t supposed to.”

It hadn’t been days, because Michael had spoken to her that morning over comms and Tilly had been fine then. Her sense of the passage of time must be off.

“Why didn’t you want to call me?” Michael asked.

Tilly shifted, and then pulled back the sleeve of her jumpsuit. She held out her arm, which had “do not call Michael!!!!!” written across it in marker.

“Okay,” said Michael. That was a little worrisome. “But why not?”

Tilly looked at her own arm, as if she might find an explanation for the warning written along side it. “I think,” she said, visibly trying to concentrate. “I think it - I think it might be a little contagious?”

“Oh,” said Michael. She tried standing up, but Tilly was still mostly on top of her and she didn’t get very far. “Oh, okay. That doesn’t actually sound anything like LSD.”

“I didn’t say it was acid!” said Tilly. “ _Like_ acid, maybe, but I don’t have that much experience with drugs, okay? Normal drugs or whatever insanity they have here. This is uncharted territory and all that for me.” She leaned forward and sighed into Michael’s neck. “I don’t deserve that Master of Poisons medal _at all_.”

“Okay,” said Michael. She realized her breathing was too rapid and she forced herself to slow it down, even it out until it could calm her down. “Okay, let’s think about this.”

But it was hard to think clearly with Tilly writhing around in her lap.

“I think I’d get better if you touched me,” said Tilly, breathing hard against Michael’s neck.

That was a dubious hypothesis if Michael had ever head one, but she was beginning to feel a little bit light-headed herself, and controlled breathing wasn’t doing anything to help. And it wasn’t as if she had any better ideas. Tilly’s jumpsuit was already open, her chest practically bursting out of low-cut tank top she wore under it, and she gasped as Michael dragged her fingers across her right breast, right over her heart.

“I’m so wet,” she said, nearly breathless, and Michael was confident it was the most openly vulgar thing Tilly had ever said. “Oh, god, I’m so wet. I’m sorry, it’s just, I love you so much, and you’re so pretty, and-“

Michael yanked down on the zipper to Tilly’s jumpsuit, right down until it stopped right above her crotch, and Tilly squeaked in surprise. Michael nudged her up. “Get out of it,” she said, and she had to help Tilly, had to drag the fabric down while Tilly climbed out of it. Tilly managed to the tank top off by herself, even uncoordinated as her movements were, and then Michael helped her with the clasp on her bra. She was fully naked by the time she turned around, pale and flushed even in the darkness of the room, and there was no timidness in her, none of the usual shyness she showed when they would get changed in the same room together.

“I don’t think I’ve ever been this turned on before,” Tilly said, and Michael nodded, her throat suddenly dry.

She leaned back onto the pillows of the couch, and gestured for Tilly to lie down on her back on top of her. She nestled her chin against Tilly’s shoulder and pushed her knee up between Tilly’s legs, nudging them further open.

“Michael,” said Tilly, panting as Michael ran a hand across the soft skin of her stomach, and then between her legs. She whimpered as Michael’s fingers pressed against her clit. “Yes, please, right there!”

She gasped as Micheal slid two fingers inside her, just long enough to get them wet before she focused back on her clit, pushing in hard circles as Tilly shifted on top of her, rocking her hips up against Michael’s hand. Michael inhaled the scent of her neck, of her hair - neither Tilly wore much in the way of perfume, and so smelled the same in both universes, something that felt familiar and right in spite of the insanity of the situation.

“We should do this all the time,” said Tilly, her voice uneven as she struggled to speak around her breathing. “Oh, we should do this every day, just absolutely all the time.”

Right at that moment it sounded like a perfectly reasonable idea to Michael. She cupped one of Tilly’s breasts with her free hand, relishing the weight of it. She slid up until she had Tilly’s nipple caught between her fingers, and Tilly whimpered again, her hands going to Michael’s wrists as if she needed something to hold onto.

“Does it always feel like this?” she asked. Her voice was shaky and rough, and Michael could feel how swollen with arousal she’d become. “I mean, is it supposed to always be like this? Or is it the myc- the whatever it is?”

“I don’t really know,” said Michael, a little amazed to find that she was still capable of speech. “We can figure it out, though.”

“Yes, yes, absolutely,” said Tilly. Michael ran her hand from Tilly’s chest down to her hips and then across her thigh, her skin so soft and warm for a second she was tempted to stop fingering her, just so she could have both hands free to feel her up. Tilly was rocking up against her insistently, though, her hand covering Michael’s as she fucked her, and Michael didn’t want to stop, not when Tilly seemed so close, so near the edge.

She came loudly, incoherent words spilling out of her mouth as she pulled her legs in, tightening around Michael’s hand. Michael held her for a moment until her cries died down and she went limp, sliding down onto the floor again.

“Oh, I was right,” she said. She looked like a mess but she sounded happy. “I do feel better.” She let her head rest against Michael’s thigh as she fumbled with the zipper on the back of Michael’s boot. “Oh, fuck, Michael. Why is this uniform so much?”

“That’s what it’s like here,” said Michael. Her fingers were still wet from being inside Tilly, and all of a sudden the only thing she could concentrate on was how wet she was. She pressed her hand between her legs but the uniform fabric was too thick for her to feel anything. “It’s all too much.”

Tilly managed to get one of her boots off and then started on the other one, tugging it free while Michael unhooked her collar and the back strap of her breastplate. It was a relief when it was finally off, and for a second she felt like she could breath again, like some great weight had been lifted.

She still felt too boneless to stand properly, but Tilly helped her, rising up to her knees to help her balance until they’d gotten everything off her. She settled back onto the couch, with Tilly on her knees between her legs, her face pressed against Michael’s thigh. Tilly kissed her, her mouth warm and wet against her skin, and Michael sighed. She spread her legs as wide as she could as Tilly dragged her mouth upwards, leaving a wet mark behind her as she licked her way to Michael’s core.

It felt Tilly was kissing her for ages, and when she finally found her pussy Michael moaned, rolling her head back against the couch cushions. She wanted to melt into feeling, to collapse entirely.

Tilly was talking, saying something to her In between licking and sucking at her clit, but it was too muffled for Michael to make anything out. It was just a vibration, something that felt nice, felt like it was meant to make her sensitive skin feel like it was electric. Everything felt erratic - her breathing, her pulse, the insisting rising throbbing in her cunt.

She crossed her legs over Tilly’s back, pulling her in closer as she dug her fingers into the fabric of the couch to try and steady herself. Outside, nearly everyone in the universe wanted to see them dead, but in here things were perfect. In here they loved each other, in here they were allowed to be happy.

Michael came, then, in a pulsing wave that started at her core and washed through the rest of her, leaving her skin sensitive and tingling from head to toe.

As Tilly climbed back onto the couch to settle in beside her some level of reason came back to her. They needed to get cleaned up, to put themselves back together, to come up with some kind of cover story if someone important wanted to know whey they’d met and what they were doing together. The longer she stayed, the more suspicious people would get, the more likely someone would come around with questions they would eventually have to answer.

It was a distant concern, though, one she was to loose and satisfied to deal with at the moment. People could wait a few hours.

“I miss you,” Tilly said. “I miss you being you. And I miss our home.”

“I know.” Michael ran her fingers through Tilly’s hair and she sighed, sounding content for the moment. “I miss it too. But we’ll get home eventually.”

She wasn’t sure how, not yet, but she knew they’d figure out.


End file.
